Cooling of propeller-shaft sterntube bearings



COOLING 0F PBOPELLER-SHAFT STERN-TUBE BEARINGS E m A T T O C 5 H FiledMarch 19, 19%

Patented Oct. 8, 1940 UNITED STATES COOLING 0F PROPELLER-SHAFT STERNTUBE BEARINGS Hubert Scott-Paine, Hythe, Southampton, EnglandApplication March 19, 1940, Serial No. 324,783

In Great Britain March 9, 1939 l 1 Claim.

The invention is for improvements in or relating to the cooling ofstern-tube bearings for boats, and particularly for small high-speedmotor boats.

The high rate of revolution of the propeller shaft in small high-speedboats makes cooling of the propeller-shaft stern tube important, and itis important also that any cooling means should be of simple and compactconstruction.

My prior specification Serial No. 269,019 describes cooling means for apropeller-shaft stern tube in which water, for cooling and lubricatingthe bearing is circulated through the bearing between the shaft and thetube from a submerged inlet, by the movement of the boat through thewater. i

The present invention comprises a combination with a high-speed boat ofa stern tube having an aft end portion spaced from the propeller shaft,a bearing for the propeller shaft in the for ward portion of the sterntube, a water jacket surrounding the stern tube in the locality of thebearing, a scoop on the bottom of the boat arranged to face forwardly,an inlet conduit connecting the scoop with the jacket, and an outletconduit connecting the jacket with the aft end portion of the sterntube.

The aft end portion of the stern tube may be open to the water along itslower side, for which purpose it may be tunnel-shaped.

The jacket may extend along a part of the aft end portion of the sterntube, in which case the outlet conduit may connect that part of thejacket which is disposed aft of the bearing with that part of the aftend portion of the stern tube which is disposed aft of the jacket.

The following is a description of a stern tube and bearing arranged fora small high-speed boat, reference being made to the accompanyingdrawing, in which:

Figure l is a vertical section along the length of the stern tube;

Figure 2 is a section on the line 22 of Figure l, and

Figure 3 is an under-plan, on an enlarged scale, of the scoop.

The stern tube is arranged in the usual position on the bottom of theinside of the boat sloping downwardly from its forward end. The tube isprovided at its aft end with a tunnel-shaped portion and with acylindrical portion 2| near its forward and upper end having a recess 22of smaller diameter than the remainder, which recess contains a whitemetal or other journal bearing 23. The tunnel-shaped part 20 is of sucha size as to be spaced away from the propeller shaft.

' The cylindrical portion Zlof the tube has, cast integrally with it, acooling jacket 24 which extends from the front end of the journalbearing to a position past the rear end so as to be half as long againas the bearing, and this jacket is, when viewed on a cross-sectiontransversely of the bearing, of substantially semi-circular formextending symmetrically circumferentially of the tube over the upperpart. A part 26 of the tube, half-way along the length of the bearing,is, however, formed solid, and a hole 27 is drilled through this partof" the tube and through the white metal bearing to serve as an inletfor the supply of grease to the bearing.

Circulation of water through the jacket is effected by aforwardly-facing scoop 28 which is screwed on the outside of the bottomof the boat to one side of the stern tube and which is connected to acopper inlet pipe 3%] by means of a joint tube of rubber Bl or othersimilar resilient material. The copper inlet pipe is attached by acoupling to a hollow plug 33 in an inlet formed in the jacketdiametrically opposite to the grease inlet.

An outlet 34 for the water from the jacket is situated at the top of,and at the aft end of, the jacket. A boss 35 formed at this point isinternally threaded at 36 to receive an externally threaded part of acontrol cock 40 which is secured to an outlet pipe 31. The outlet pipeis connected to a similar boss 3% formed on the stern tube abouthalf-way between the lower end of the bearing and the lower end of thetube by means of a screw plug and coupling 39. The scoop 28 is made ofsuitable sea-water resisting material and is fitted by wood screws illin a watertight manner to the bottom of the boat so as normally to besubmerged.

When the boat is in motion, water is forced into the scoop and throughthe copper inlet pipe into the jacket formed round the stern tube, andthen passes out at the lower end of the jacket at the top thereof and isdischarged into the top of the stern tube at a position aft of thejacket; thus, the cooling water is employed to cool the greaselubricatedbearing at the forward part of the tube and also to cool the after endof the propeller shaft itself.

The shape and size of the scoop or scoops will be such as to extract asubstantial flow of sea water for a given minimum speed of the boat, sothat at higher speeds of revolution of the shaft corresponding togreater speeds of the boat, a greater supply of cooling water iscirculated.

Thus, the apparatus described provides an efficient means for coolingthe stern tube-bearing Which also satisfies the requirements ofsimplicity and compactness necessitated by a small boat.

I claim:

For use in combination with the propeller shaft of a high-speed boat, astern tube having a tunnel-shaped aft end portion spaced from thepropeller shaft and open to the water along its lower side, a bearingfor the propeller shaft in the for Ward portion of said stern tube, awater-jacket surrounding said stern tube in the locality of said bearingand extending along a part of the portion of the stern tube which is aftof said bearing, an inlet conduit connected to that part of saidwaterjacket which surrounds the stern tube in the vicinity of saidbearing, and an outlet conduit connecting that part of said water-jacketwhich is disposed aft of said bearing with that part of thetunnel-shaped portion of the stern tube which is disposed aft of saidjacket.

HUBERT SCOTT-PAINE.

